Vents on indirect radiators, time to replace?

kacrejam

I have a 2-pipe steam system with 4 indirect radiators mounted in basment.  I'm wondering whether it's time to replace the vents?  As well what kind/manufacturer I should use?  There seems to be several different types of vents either original or replaced a long time ago.  You can see the different vents in the pictures.

nicholas bonham-carter

2pipe vents

normally, a 2-pipe system has traps to remove the air, and allow the steam in. maybe you can draw a diagram of the piping layout.

the small diameter of the supply pipes i see may indicate a low-pressure vapor system, and these had various means of venting. in short, your vents are looking tired, but i am not sure they are in the right place.--nbc

Carl1979

wow! thats some fancy boxes

you got for your indirect radiators. I have one in my basement its a big ugly metal box I consider it the monster in the corner . I don't have a answer for the venting question you asked about . but you may have another venting concern even more important '



How ? is air getting into those boxes are they still vented to the outside. mine was, Intake vent hidden under a porch. its a incredible wasteful practice . I disconnected mine and it gets its air directly from the basement now. Just something I wanted to be sure you where aware of.

Dave in QCA

Proper vents

My understanding of the common piping practice for indirect radiators on a two pipe system, is that they were not trapped like the radiators on the floors above, but rather, they had 3 connections.  One was the steam supply.  The second was a drip leg that connected to a wet return.  The third was a vent line.  The vent line commonly went through and air service valve, such as a Paul valve, connected to a dry return.  Connection to the dry return was important if the system was designed to operate with a vacuum pump, or otherwise operate with a vacuum produced in the return line.  If it was not going to operate in a vacuum, then a vent to the atmosphere might have been used.



I am not sure of the purpose of this setup on the piping other than there might be a loss of the dimension B because these indirects are situated at a lower level that other devices in the system. At any rate, the drip and air valve connections are my understanding of the connections as per comments from Steamhead.



What vent is proper?  It looks like you have 3 different vents in place.  I would assume that the green vent that looks like a #75 could be a #74.  You also have a Hoffman 4A.  The third vent appears to be an obsolete vent, I think it was called a Quick Vent, and I'm not sure if it was Hoffman or another manufacturer.  Are your vents working now?  Do they vent?  Do they close when steam gets to them or to they keep hissing and blowing steam?   Do the indirects heat up at about the same rate?  If the vents are working, there is no need to replace them.  If they are working and the indirects are heating evenly, but the vents don't close when steam gets to them, you can probably fix them by soaking in vinegar or limeaway cleaner.  If I was having to select a replacement, I think I would go the direction of the 4A.  It is midway in the venting rates of the possible vents you could use.  You want to vent adequately, but not too fast.

kacrejam

Fresh-air

There was an impresive outside air wooden duct system that used to feed these indirect radiators.  One of the windows in the basement received the outside air and fed to these.  I'm not using that fresh air duct system anymore.  Just the basement air.  I do get concerned that there is enough air recycling down to the basement to keep the flow going but it does seem to be working well.

kacrejam

Wow

Wow, thats pretty amazing.  You named all the vents correctly - I just checked.  The first big green one is a Hoffman N-75.  I'm not sure how well these vents are working.  I don't hear any hissing when the steam is on.  I don't hear them shut-off or anything like that.  I am able to feel that at least some of the indirects are heating well.  However, One of them does not seem to heat up like the others.  This one is slightly farther down the line and has a Hoffman N-75.  I'm thinking I will take you advice and get a 4As installed.

Dave in QCA

vent ratings

The Hoffman 75 is a Main Vent, and it vents at .5 CFM at 1oz of pressure. (Very fast for a radiator vent!) The 4A vents at .133 CFM at 1 oz.  If I were you, I'd try to evaluate which indirect is heating about right.  Not too much, not too little.  I suspect the one with the Hoffman 75 is heating too much.  It is probably not unusual for the vents to get hot enough to close unless you boiler is running a very long time.  Those indirects generally have more capacity than common radiators and may take longer to heat up.  Of course, you have to keep in mind that they were designed to be able to heat very old air from outdoors and to deliver it to your rooms has HOT air for heating.  Now that you are using basement air, their capacity is larger than is needed, so slow / partial heating is probably a good thing, otherwise the rooms that are heated from the indirects would get too warm.